<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
    <head>  
    <meta name="DEscription" contect="my code demo" />  
    <meta name="Author" contect="Michael@www.micmiu.com" />  
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
    <title>js check file size </title>  
    </head>  
    <body>  
        <img id="tempimg" dynsrc="" src="" style="display:none" />  
        <input type="file" name="file" id="fileuploade" size="40" />  
        <input type="button" name ="check" value="checkfilesize" onclick="checkfile()"/>  
   
    </body>  
    <script type="text/javascript">  
        var maxsize = 2*1024*1024;//2M  
        var errMsg = "上传的附件文件不能超过2M！！！";  
        var tipMsg = "您的浏览器暂不支持计算上传文件的大小，确保上传文件不要超过2M，建议使用IE、FireFox、Chrome浏览器。";  
        var  browserCfg = {};  
        var ua = window.navigator.userAgent;  
        if (ua.indexOf("MSIE")>=1){  
            browserCfg.ie = true;  
        }else if(ua.indexOf("Firefox")>=1){  
            browserCfg.firefox = true;  
        }else if(ua.indexOf("Chrome")>=1){  
            browserCfg.chrome = true;  
        }  
        function checkfile(){  
            try{  
                var obj_file = document.getElementById("fileuploade");  
                if(obj_file.value==""){  
                    alert("请先选择上传文件");  
                    return;  
                }  
                var filesize = 0;  
                if(browserCfg.firefox || browserCfg.chrome ){  
                    filesize = obj_file.files[0].size;  
                }else if(browserCfg.ie){  
                    var obj_img = document.getElementById('tempimg');  
                    obj_img.dynsrc=obj_file.value;  
                    filesize = obj_img.fileSize;  
                }else{  
                    alert(tipMsg);  
                return;  
                }  
                if(filesize==-1){  
                    alert(tipMsg);  
                    return;  
                }else if(filesize>maxsize){  
                    alert(errMsg);  
                    return;  
                }else{  
                    alert("文件大小符合要求");  
                    return;  
                }  
            }catch(e){  
                alert(e);  
            }  
        }  
    </script>  
</html>